On Mon, Apr 20, 2020 at 3:11 PM Johannes Weiner <hannes@xxxxxxxxxxx> wrote: > > The memcg charging API carries a boolean @compound parameter that > tells whether the page we're dealing with is a hugepage. > mem_cgroup_commit_charge() has another boolean @lrucare that indicates > whether the page needs LRU locking or not while charging. The majority > of callsites know those parameters at compile time, which results in a > lot of naked "false, false" argument lists. This makes for cryptic > code and is a breeding ground for subtle mistakes. > > Thankfully, the huge page state can be inferred from the page itself > and doesn't need to be passed along. This is safe because charging > completes before the page is published and somebody may split it. > > Simplify the callsites by removing @compound, and let memcg infer the > state by using hpage_nr_pages() unconditionally. That function does > PageTransHuge() to identify huge pages, which also helpfully asserts > that nobody passes in tail pages by accident. > > The following patches will introduce a new charging API, best not to > carry over unnecessary weight. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>
